Only a few days late but freaking out PLEASE COMMENT

So my last period started on august 12th and I was supposed to get my next one on September 7th and I still haven't gotten it. I know it's kinda dumb to be freaking out when it's only a couple days late but I'm usually right on schedule.

My boyfriend and I only had sex like twice since my last period and we used a condom both times. I don't really think I'm pregnant but I'm just really worried. I'm almost never late and I don't know what could be causing it.